As demand for information services has increased over the last decade, the technology to meet the demand has increased accordingly. Approximately ten years ago a modem, typically a commercial product, provided data transfer rates of around 2.4 kilobits per second ("KBPS") over analog telephone lines. Currently high-speed modems and ISDN terminal adapters coupled over a public switched telephone network provide data transfer rates of between 28.8 and 128 KBPS for both commercial and residential customers. Internet service providers are currently seeking technology that will furnish customers with faster transfer rates for reducing download time. In addition the evolution of digital television and other video developments has increased the demand for higher data transfer rates, such as a megabits per second ("MBPS") transfer rate. These higher data transfer rates are sometimes called "broadband service" or MBPS service. The MBPS service typically provides for both upstream and downstream data transfer and may be referred to as interactive broadband service ("IBS").
The 1996 Telecommunications Deregulation Act allows a variety of providers to compete for IBS. The providers currently considered as leaders in meeting the IBS needs of consumers include long distance carriers, local carriers and cable companies. In order to provide IBS, resource sharing and partnerships may develop among a variety of businesses.
There are currently four technologies being considered as contenders to provide IBS or similar service. These technologies include techniques for using the existing twisted pairs of wires in the current telephone network, coaxial cables, fiber links, and wireless links. A detailed discussion of these technologies can be found in IEEE Network Magazine, Special Issue on Broadband Services to the Home, Vol. 11, No. 1, January/February, 1997. Each of these technologies shows promise towards providing IBS, but each technology has technical problems and economic constraints. An access network that can provide for a complex mix of broadband services such as a high-speed internet connection, video on demand, telecommuting, and future applications is currently being developed incorporating these four technologies. Selection of the best or optimum technology is dependent on a variety of parameters such as the infrastructure of a country, the physical environment for a new installation, the demographic diversity of users and other factors.
Although the above four technologies are expected to provide IBS to a large number of subscribers, the use of a power system network may be capable of serving as an IBS technology. Currently a partnership exists between local telephone service providers and power companies. In a typical residential location a support pole or telephone pole is used as part of the structure for providing for getting both power lines and telephone lines to a customer. Cable television ("CATV") providers recently joined the partnership in order to have poles to support coaxial cables. Because of recent asymmetric digital subscriber line development, some local telephone companies may be able to deliver television programming over existing and new telephone lines. Further it has been discovered that part of the excess bandwidth on television cables of CATV companies can be used to provide telephone and data service.
As power companies look for new sources of revenue and demands for data bandwidth increase, the use of power system networks may be a means for providing IBS. Currently, existing power line communication systems are limited to low data rates which are used for monitoring and controlling functions in the power system network. These existing systems are called power line carrier communication systems. Power line carrier communications systems use conventional high-voltage transformers to couple communications signals to and from the high-voltage lines of a power system. The high-voltage transformers are expensive and typically limited to coupling signals having frequencies between 30 hertz and 50 kilohertz. Because of cost and bandwidth limitations, power line carrier communication systems are not suitable for IBS.
In order to use high-voltage lines for IBS there are a variety of problems to consider. For a power line to provide high-speed data service there must be an apparatus and method for efficiently coupling radio-frequency signals to the high-voltage cables of the power network. Further the apparatus and method should not compromise the performance of the existing power system and must have a means to isolate the low-voltage electronic components required to process radio-frequency signals transporting data. In addition such a coupling apparatus must be inexpensive, small, environmentally acceptable, essentially maintenance free and easy to install.